This is one of my absolute favorite games, and a must-have for the Tolkien fan. It thematically does a very good job of marrying the themes for each side (the desparate push for the free peoples, and the crushing military for the Shadow). Because of the way event cards are used, the same strategy won't always work for each player so you do have adjust on the fly. And they all add good thematic points to the game.
I'd plan 4-5 hours for your first play, and be ready to spend 40 minutes for the first setup. It moves a lot faster once you know the map layout and understand the way the nations are distributed, but that may take a game or two (if not for you, for your not-as-big-a-Tolkien-reader opponent).
But I highly recommend it- one of my absolute favorite games.